1. Field of the Invention
This invention relates to switchgear assemblies for electric power distribution systems. More particularly, it relates to the neutral bus of such switchgear assemblies and arrangements for mounting such neutral bus within the cabinet of the assembly and connecting such neutral buses of adjacent units.
2. Background Information
Switchgear assemblies for electric power distribution systems include electrical apparatus housed in metal cabinets with associated conductors including bus bars and cabling for connecting the electrical apparatus in appropriate locations within the distribution system. Typically, the electrical apparatus includes switching devices such as circuit breakers or network protectors which provide protection, disconnect switches for isolating parts of the distribution system and transfer switches for connecting the distribution system to alternative power sources. The electrical apparatus can also include instrumentation such as metering equipment.
The associated conductors typically include a set of rigid multi-phase buses extending transversely through the cabinet. This set of rigid transverse buses usually includes a neutral bus, although in most installations in the United States the neutral is not switched.
Many installations require multiple cabinets arranged side by side, each with a transverse set of rigid buses. It is common to assemble several cabinets as a unit for shipping with a common set of buses extending transversely through the unit. Such practice requires that the set of transversely extending buses in adjacent units be connected in the field. As the rigid buses extend through the middle of each cabinet, it is not easy to make such connections, especially in the case of the neutral bus which is typically fabricated as a stack of elongated flat conductors set on edge and horizontally spaced. The splice connection between the neutral buses in adjoining units is made by a set of short sections of flat conductor interleaved between and secured to the two sets of flat conductors by bolts. This requires the manipulation of a number of small parts in restricted space.
The conductors provided within each cabinet include runbacks for the phase and neutral conductors which extend rearward into another compartment for connection to cabling forming a second set of buses to which the electrical apparatus is connected. The neutral runbacks are also fabricated as a stack of elongated, flat conductors set on edge and horizontally spaced which butt against the side of the rearmost conductor of the transverse neutral bus. Such a joint requires electrically conductive spacers between the flat conductors of the transverse bus and associated fasteners. Again, this requires manipulation of a number of small parts, although such joints are usually made during assembly at the factory.
There is room for improvement therefore in the neutral bus and its mountings within switchgear.